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Fragile X syndrome co-occurs with autism in many cases and is a suspected genetic cause of the autism in these cases. [11] [22] This finding has resulted in screening for FMR1 mutation to be considered mandatory in children diagnosed with autism. [11]
It was so named because one part of the X chromosome has a defective piece that appears pinched and fragile when under a microscope. Fragile X syndrome affects about two to five percent of people with ASD. [40] If one child has Fragile X, there is a 50% chance that boys born to the same parents will have Fragile X (see Mendelian genetics ...
Down syndrome is a genetic condition in which people are born with an extra copy of chromosome 21. This extra copy affects the development of the body and brain, causing a range of physical and mental impairments for the individual. Fragile X syndrome, most frequent among males, is thought to cause autism and intellectual disability.
Other terms used to describe regression in children with autism are autism with regression, autistic regression, setback-type autism, and acquired autistic syndrome. [16] Within the regressive autism developmental course, there are two patterns. The first pattern is when developmental losses occur in the first 15 months to 3 years.
Examples of autism that has arisen from a rare or de novo mutation in a single-gene or locus include neurodevelopmental disorders like fragile X syndrome; metabolic conditions (for example, propionic acidemia); [64] and chromosomal disorders like 22q13 deletion syndrome and 16p11.2 deletion syndrome. [65]
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder most frequently seen in male premutation carriers of Fragile X syndrome (FXS) over the age of 50. [ 4 ] [ 5 ] The main clinical features of FXTAS include problems of movement with cerebellar gait ataxia and action tremor .
Less commonly known genetically determined neurodevelopmental disorders include Fragile X syndrome. Fragile X syndrome was first described in 1943 by Martin and Bell, studying persons with family history of sex-linked "mental defects". [43] Rett syndrome, another X-linked disorder, produces severe functional limitations. [44] Williams syndrome ...
Some ASD is associated with clearly genetic conditions, like fragile X syndrome, but only around 2% of autistic people have fragile X. [123] Hypotheses from evolutionary psychiatry suggest that these genes persist because they are linked to human inventiveness, intelligence or systemising. [197] [198]